The present disclosure relates to a technical field of displays, and more particularly to an AMOLED pixel driving circuit and pixel driving method.
Organic light emitting diode (OLED) display devices have advantages of being self-luminous, having a low driving voltage, high luminous efficiency, short response time, high sharpness and contrast, a nearly 180° view angle, and a wide operating temperature range, and allowing implementation of flexible displays and large area full color displays, etc., and have become display devices with the most development potential.
Conventional active-matrix organic light-emitting diode (AMOLED) pixel driving circuits usually have a 2T1C structure, i.e., a structure of two thin film transistors plus a capacitor, which converts voltage into current.
As illustrated in FIG. 1, an existing AMOLED pixel driving circuit with a 2T1C structure includes a first thin film transistor T10, a second thin film transistor T20, a capacitor C10, and an organic light emitting diode D10. The first thin film transistor T10 is a driving thin film transistor. The second thin film transistor T20 is a switch thin film transistor. The capacitor C10 is a storage capacitor. Specifically, a gate of the second thin film transistor T20 receives a scan signal Gate, a source of the second thin film transistor T20 receives a data signal Data, and a drain of the second thin film transistor T20 is electrically coupled to a gate of the first thin film transistor T10. A source of the first thin film transistor T10 receives a positive power supply voltage OVDD, a drain of the first thin film transistor T10 is electrically coupled to an anode of the organic light emitting diode D10, and a cathode of the organic light emitting diode D10 receives a negative power supply voltage OVSS. A terminal of the capacitor C10 is electrically coupled to the gate of the first thin film transistor T10, and another terminal of the capacitor C10 is electrically coupled to the source of the first thin film transistor T10. When the 2T1C pixel driving circuit is driving the AMOLED, a current flowing through the organic light emitting diode D10 satisfiesI=k×(Vgs−Vth)2,where I is the current flowing through the organic light emitting diode D10, k is an intrinsic conductivity factor of the driving thin film transistor, Vgs is a voltage difference between the gate of the first thin film transistor T10 and a source of the first thin film transistor T10, Vth is a threshold voltage of the first thin film transistor T10. It can be seen that the current flowing through the organic light emitting diode D10 is related to the threshold voltage of the driving thin film transistor.
Due to reasons, such as an unstable manufacturing process, a threshold voltage of a driving thin film transistor of each pixel driving circuit in a panel is different. Even if a same data voltage is applied to the driving thin film transistor of each pixel driving circuit, the current flowing through an organic light emitting diode of each pixel driving circuit still may not be the same, thereby affecting uniformity of image displaying quality. Furthermore, as driving time of a driving thin film transistor becomes longer, aging and variation of material of the driving thin film transistor may appear, causing a threshold voltage of the driving thin film transistor to drift. Further, a degree of aging of material of each driving thin film transistor may be different, and a drift amount of a threshold voltage of each driving thin film transistor may also be different, causing the panel to display non-uniformly. Also, aging and variation of the material of the driving thin film transistor may cause a turn on voltage of the driving thin film transistor to increase, and a current flowing through an organic light emitting diode to decrease, resulting in problems such as decreased luminance and lowered luminous efficiency of the panel.
Therefore, it is desired to provide an AMOLED pixel driving circuit and pixel driving method to solve the problems existing in the prior art.